1. Field of the Invention
The present invention relates to a photometric sensor which performs photometry by using a plurality of photoelectric conversion elements, and which outputs photometric signals in time series.
2. Description of the Related Art
A photometric sensor is per se known, which performs photometry by using a plurality of photoelectric conversion elements, and which outputs photometric signals in time series (refer to Japanese Patent Laid-open Application No. 63-168613).
FIG. 8 is a functional block diagram showing the overall construction of an example 1 of this type of photometric sensor. Referring to this figure, a photoelectric conversion section 2 comprises a plurality of photoelectric conversion elements 3a through 3g arranged in a one dimensional array, and a CCD (Charge Coupled Device) shift register 4 for transmitting electric charges. Each of the photoelectric conversion elements 3a through 3g generates and accumulates electric charge according to the strength of the light which is incident upon it. The CCD shift register 4 comprises a plurality of CCD elements 4a through 4g provided in respective correspondence to the photoelectric conversion elements 3a through 3g, and a pair of relay CCD elements 4h and 4i provided for relay purposes which do not correspond to any of the photoelectric conversion elements 3a through 3g. Each of the former CCD elements 4a through 4g receives the electric charge which has been accumulated by its corresponding one of the photoelectric conversion elements 3a through 3g and transmits it. On the other hand, the latter relay CCD elements 4h and 4i relay to a charge to voltage conversion circuit 6 the electric charges transmitted from the CCD elements 4a through 4g which they receive. A control section 5 controls these processes of electric charge accumulation and charge transmission via the CCD shift register 4 performed by the photoelectric conversion section 2. Further, the charge to voltage conversion circuit 6 converts the electric charges which are output in order from the CCD shift register 4 into a voltage signal Vout.
These electric charges which have been accumulated are output from the CCD shift register 4 upon the input of a clock pulse .PHI.1 which is transmitted from a clock pulse generator not shown in the figure, and by the charge to voltage conversion circuit 6 are output to an A/D converter 8 after being converted into the voltage signal Vout. At this time, a timing signal ADT is output from the control section 5 to the A/D converter 8 in order to initiate A/D conversion. The A/D converter 8 performs A/D conversion of the voltage signal Vout at a timing determined by the receipt of the timing signal ADT, and a microcomputer 7 performs photometric calculations based upon the photometric data which are A/D converted in this manner into a digital signal.
Further, it can also happen that, while the relay CCD elements 4h and 4i of the CCD shift register 4 are inputting the electric charges directly from the photoelectric conversion elements 3a through 3g, initial electric charges also are from the beginning in existence upon these relay CCD elements 4h and 4i. Although these initial electric charges on the relay CCD elements 4h and 4i represent meaningless data, during charge transmission this meaningless data is also output in order from the photometric sensor 1 according to the timing signal ADT. In the exemplary photometric sensor shown in FIG. 8 and described above, in order, first the meaningless data item arising from the initial electric charge upon the relay CCD element 4i is output, next the meaningless data item arising from the initial electric charge upon the relay CCD element 4j is output, and subsequently the photometric data items arising as the results of the processes of photoelectric conversion performed by the photoelectric conversion elements 3g, 3f, . . . are output in sequence. Because the data from these relay CCD elements 4h and 4i is data which is not required, this unnecessary data due to the relay CCD elements 4h and 4i must be extracted and deleted from the data read out in order from the CCD shift register 4.
In this connection, in the case of a prior art photometric sensor 1, the position of the relay CCD elements 4h and 4i upon the CCD shift register 4 for electric charge transmission is recorded in advance in the memory of the microcomputer 7, and the data from the relay CCD elements 4h and 4i (which is not required) is extracted and is deleted from among the data input from the CCD shift register 4 via the A/D converter 8, so that only the photometric data from the photoelectric conversion elements 3a through 3g is read in by the microcomputer 7 and is used for performing the processes of photometric calculation.
In a prior art photometric sensor of the type described above the photoelectric conversion elements are arranged in a one dimensional array, and, since also a certain number of such relay CCD elements are provided for example at the leading end and/or at the trailing end of the CCD shift register, it is comparatively easy for the microcomputer to distinguish the data arising from these relay CCD elements, which is not required.
However, with a photometric sensor of the type in which a plurality of photoelectric conversion elements are arranged in a two dimensional array and perform photoelectric conversion over a two dimensional plane surface, it is necessary to provide, not only a plurality of linear CCD shift registers each extending for example along the X axis direction and collecting electric charges from a plurality of photoelectric conversion elements, but also another CCD shift register extending for example along the Y axis direction and collecting the electric charges which are transmitted from these X axis CCD shift registers. In this type of construction, since relay CCD elements are provided for the various CCD shift registers in a similar manner to that outlined above, various items of meaningless data, which are not required, arising from the initial charges on these relay CCD elements come to be mixed into the data signals output from the Y axis direction CCD shift register, along with the items of photometric data from the photoelectric conversion elements, which are required, in a relatively complex manner. For this reason, the processing required from the microcomputer in order to eliminate these meaningless data items becomes relatively complicated, and a problem arises with regard to the amount of processing time required.